Fish

Not everything lasts forever

Times will change

Things will go and we'd feel deranged

As the world's state flips like a lever

Time goes by and we can't help it. There will be times with plenty of fish. Other times there isn't enough fish to go around. The expression is used for comfort, mainly in the world of dating. It can't be accurate, the world will always change. We evolve. We adapt. Overtime, we will not be the same person we were once before. Nothing is exact, there is always probability. There can't always be plenty of fish in the sea, when the sea constantly changes.